A hydrogenated norbornene-based ring-opening copolymer exhibits excellent optical properties, weatherability, electrical properties, and the like, and is used in a wide variety of fields (e.g., optical material). Since the hydrogenated norbornene-based ring-opening copolymer exhibits excellent humidity resistance, transparency, heat resistance, chemical resistance, and the like, the hydrogenated norbornene-based ring-opening copolymer is also suitably used in the field of a packaging film used for food, a drug, and the like.
It is known that a hydrogenated product of an amorphous polar group-containing norbornene-based ring-opening polymer obtained using a norbornene-based monomer that includes a polar group exhibits excellent adhesion to a metal.
However, the hydrogenated product of the amorphous polar group-containing norbornene-based ring-opening polymer exhibits inferior humidity resistance and the like due to the polar group.
In order to solve this problem, Patent Literature 1 proposes a graft modification technique using a solution method or a melt method that hydrogenates a non-polar norbornene-based ring-opening polymer produced using a norbornene-based monomer that does not include a polar group to obtain a hydrogenated product, and reacts the hydrogenated product with a polar group-containing compound that includes an ethylenically unsaturated bond (e.g., maleic anhydride) in the presence of a radical initiator. According to the method disclosed in Patent Literature 1, it is possible to reduce the amount of polar group introduced into the polymer. In the example of Patent Literature 1, graft modification is effected in cyclohexane to obtain a modified product, and the modified product is coagulated using acetone, separated, and dried to obtain a hydrogenated product of an amorphous polar group-containing norbornene-based ring-opening polymer, which is dissolved in a solvent together with a cross-linking agent to obtain a cross-linkable resin composition.